1. Field Of The Invention
The present invention relates to a process-liquid supply system and a process-liquid supply method, in which a remaining amount of a process liquid in a container tank is measured by a level sensor disposed on a level gauge pipe.
2. Description Of Related Art
A level gauge pipe provided with a level sensor is connected to a container tank, such as a supply tank that contains a process liquid to be supplied to a substrate processing part, and a preparation tank where the process liquid is prepared, such that a remaining amount of the process liquid contained in the container tank can be measured.
The level sensor includes an upper limit sensor that detects whether the process liquid in the container tank exceeds a predetermined upper limit amount, an intermediate sensor that detects whether the process liquid falls within a predetermined normal amount, and a lower limit sensor that detects whether the process liquid falls below a predetermined lower limit amount (see, JP2001-168079A, for example).
When a remaining amount of the process liquid in the container tank is measured, there is a possibility that, depending on a kind of the process liquid, bubbles are generated on a liquid surface of the process liquid in the level gauge pipe, or that air bubbles are generated in the process liquid in the level gauge pipe. Thus, it is necessary to select a type of the level sensor depending on a kind of the process liquid.
When the mere selection of a type of the level sensor is insufficient, two level sensors may be provided. Namely, when bubbles tend to be generated on the liquid surface, the upper limit sensor and the intermediate sensor may be doubly provided. On the other hand, when air bubbles tend to be generated in the process liquid, the lower limit sensor and the intermediate sensor may be doubly provided.